1. Field of the Invention
The present invention relates to an opto-electric hybrid module including an optical waveguide section and an opto-electric conversion substrate section with a semiconductor chip for opto-electric conversion mounted therein, and to a method of manufacturing the same.
2. Description of the Related Art
As shown in FIG. 6, an opto-electric hybrid module is constructed by individually producing an opto-electric conversion substrate section E0 including a sealing resin portion 69, and an optical waveguide section W0, and then bonding the sealing resin portion 69 of the opto-electric conversion substrate section E0 to a surface of the optical waveguide section W0 with a transparent adhesive layer B therebetween, as disclosed, for example, in Japanese Published Patent Applications Nos. 2006-17885 and 2007-286289. In the opto-electric conversion substrate section E0, a semiconductor chip 67 for opto-electric conversion is mounted on a substrate 65 with an electrode 66 formed thereon, and the semiconductor chip 67 and the electrode 66 are electrically connected to each other with a bonding wire 68. To protect the bonding wire 68, a transparent resin (the sealing resin portion 69) seals the semiconductor chip 67 and the electrode 66 together with the bonding wire 68. In the optical waveguide section W0, on the other hand, a core 62 for transmitting light is sandwiched between an under cladding layer 61 and an over cladding layer 63. A cut 64 of an inverted V shape extending through the core 62 to the over cladding layer 63 at its tip is formed, as shown, in an opposite surface of the under cladding layer 61 from the core 62. The cut 64 has a cut surface provided in the form of a surface inclined at 45 degrees to the axial direction (or the longitudinal direction) of the core 62. Portions of the core 62 intercepted by the cut 64 are exposed or uncovered at the inclined surface, and the inside one of the exposed portions of the core 62 serves as a reflecting surface 62a. The bonding of the opto-electric conversion substrate section E0 and the optical waveguide section W0 is achieved using the transparent adhesive layer B between a surface portion of the over cladding layer 63 corresponding to the reflecting surface 62a in the optical waveguide section W0 and the sealing resin portion 69 in the opto-electric conversion substrate section E0. The semiconductor chip 67 is either a light-emitting element or a light-receiving element including a light-emitting section 67a or a light-receiving section formed on an opposite surface thereof from the substrate 65 (a lower end surface thereof as seen in FIG. 6).
The propagation of a light beam L in the opto-electric hybrid module is done in a manner to be described below. When the semiconductor chip 67 is a light-emitting element, a light beam L is emitted downwardly from the light-emitting section 67a of the semiconductor chip 67. The light beam L passes through the sealing resin portion 69 and the adhesive layer B and then through the over cladding layer 63 of the optical waveguide section W0, and enters the core 62. Subsequently, the light beam L is reflected from the reflecting surface 62a, and travels through the interior of the core 62 in the axial direction. Then, the light beam L exits from a front end surface of the core 62.
On the other hand, when the semiconductor chip 67 is a light-receiving element, a light beam travels in a direction opposite from that described above, although not shown. The light beam enters the core 62 through the front end surface of the core 62. Next, the light beam travels through the interior of the core 62 in the axial direction, and is reflected upwardly from the reflecting surface 62a. Then, the light beam passes through the over cladding layer 63 and then through the adhesive layer B and the sealing resin portion 69, and thereafter is received by the light-receiving section of the semiconductor chip 67.
When the semiconductor chip 67 is the light-emitting element, the light beam L emitted from the light-emitting section 67a of the semiconductor chip 67 diverges in the course of the propagation of the light beam L. For this reason, if there is a long distance D between the light-emitting section 67a of the semiconductor chip 67 and the reflecting surface 62a formed in the core 62, the light beam L diverges widely. As a result, the light beam L deviates away from the reflecting surface 62a and is not guided into the core 62 in some cases. Likewise, when the semiconductor chip 67 is the light-receiving element, the light beam traveling through the interior of the core 62 and reflected from the reflecting surface 62a also diverges. For this reason, the light beam L deviates away from the light-receiving section of the semiconductor chip 67 and is not received by the light-receiving section in some cases. It is therefore necessary to design the opto-electric hybrid module so as to minimize the distance D between the light-emitting section 67a or the light-receiving section of the semiconductor chip 67 and the reflecting surface 62a formed in the core 62.
In the conventional opto-electric hybrid module, however, the sealing resin portion 69 of the opto-electric conversion substrate section E0 is simply stacked and bonded onto the over cladding layer 63 of the optical waveguide section W0 with the adhesive layer B therebetween, as disclosed in Japanese Published Patent Applications Nos. 2006-17885 and 2007-286289. This has been common technical practice. In the opto-electric hybrid module having such a structure, it is impracticable to further shorten the distance D between the light-emitting section 67a or the light-receiving section of the semiconductor chip 67 and the reflecting surface 62a formed in the core 62. In other words, it is impracticable to further reduce optical losses between the opto-electric conversion substrate section E0 and the optical waveguide section W0. The distance D between the lower end surface (the light-emitting section 67a or the light-receiving section) of the semiconductor chip 67 and the center of the reflecting surface 62a (the axis of the core 62) is typically 200 μm or greater.